Hmmm.. I'm not sure if Slikstik makes an adapter to interface the controls with a Dreamcast. I've looked, and all I've found are interfaces that allow you to use your Dreamcast controller on your computer which isn't going to help you.
I posted a similar topic a few posts down about putting a Dreamcast in a cabinet, and other than using the BYOA X-Arcade kit, or hacking Dreamcast control pads yourself, I don't think there's any other way to do it.
Check out the other post though... it may give you a few leads....